Pyridyl compounds and pharmaceutical compositions containing them

ABSTRACT

The present invention is concerned with new pyridine double esters of formula (I), their acids, and pharmaceutically acceptable salts. These compounds can be obtained by oxydation of the corresponding 1,4-dihydropyridines, and they are useful as cardioprotective agents in pharmaceutical compositions.

The present invention relates to a series of new pyridine derivatives,their preparation procedures, their use as cardioprotective agents, andthe pharmaceutical compositions containing said derivatives. Moreparticularly, the object of the present invention is constituted bypyridine derivatives of general formula (I), in which

X represents H, NO₂, OH, CN, F, Br, Cl, CF₃, —NH—CO—CH₃, 2,3-Cl₂,2,3-(OCH₃)₂, 4-Cl, 3-NO₂ and 2-[CH═CH—COO—C(CH₃)₃], and the fused cycle2,3-oxadiazole [2,3-(═N—O—N═)];

Y represents an alcoxycarbonyl fragment R³OOC—, where R² can be H, asmall alkyl group, 2-methoxyethyl, 2-tetrahydrofurfuryl or5,5-dimethyl-1,3,2-dioxaphosphorinan-2-yl;

R represents H, an small alkyl group or, alternatively, the followingfragments: 2-methoxyethyl, 2-(benzyl-methylamino)ethyl,2-tetrahydrofurfuryl, 5-oxotetrahydrofurfuryl,3-[(4,4-diphenyl)-piperidinyl]propyl, (R)-1-benzyl-3-piperidinyl,2-(N-benzyl-(N-phenylamino)ethyl, (S)-1-benzyl-3-pirrolidinyl,2-[(4-diphenylmethyl)-1-piperazinylethyl, 3-phenyl-2-propenyl,dually-amino-alkyl, 2-(N-morpholino)ethyl or1,3-di(N-morpholino)isopropyl

R′ represents CH₃, CN or —CH₂—O—(CH₂)₂—NH₂, as well as the correspondingoptical isomers, and the pharmaceutically acceptable salts of the saidcompounds.

As non-limiting examples, the following compounds corresponding toformula (1) of the present invention can be mentioned:

4-(2,3-Dichloro-phenyl)-2,6-dimethyl-pyridine-3, 5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

2,6-Dimethyl-4-(3-fluorophenyl) pyridine-3, 5-dicarboxylic acid 3-methylester 5-(tetrahydrofuran-2-ylmethyl) ester

4-(3-Acetylaminophenyl)-2,6-dimethyl pyridine-3, 5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester (hydrochloride)

2,6-Dimethyl-4-(3-hydroxyphenyl) pyridine-3, 5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester (hydrochloride)

2,6-Dimethyl-4-phenyl-pyridine-3, 5-dicarboxylic acid 3-methyl ester5—(tetrahydrofuran-2-ylmethyl) ester

2,6-Dimethyl-4-(3-nitrophenyl)-pyridine-3, 5-dicarboxylic acid3,5-di(tetrahydrofuran-2-ylmethyl) ester (hydrochloride)

4-(3-Cyanophenyl)-2,6-dimethyl pyridine-3, 5-dicarboxylic acid 3-methylester 5-(tetrahydrofuran-2-ylmethyl) ester

2,6-Dimethyl-4-(3-nitrophenyl) pyridine-3, 5-dicarboxylic acid 3-methylester 5-(tetrahydrofuran-2-ylmethyl) ester

2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3, 5-dicarboxylic acid 3-methylester 5-(tetrahydrofuran-2-ylmethyl) ester

4-(4-Chloro-3-nitrophenyl)-2,6-dimethyl pyridine-3, 5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

4-(3-Bromophenyl)-2,6-dimethyl pyridine-3, 5-dicarboxylic acid3,5-di(tetrahydrofuran-2-ylmethyl) ester

2,6-Dimethyl-4-(3-trifluoromethylphenyl) pyridine-3, 5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

4-(2-Chlorophenyl)-2,6-dimethyl pyridine-3, 5-dicarboxylic acid 3-methylester 5-(tetrahydrofuran)-2-ylmethyl) ester

2,6-Dimethyl-4-(2-trifluoromethylphenyl) pyridine-3, 5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

2,6-Dimethyl-4-(2,3-dimethoxyphenyl) pyridine-3, 5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

4-(3-Chlorophenyl)-2,6-dimethyl pyridine-3, 5-dicarboxylic acid 3-methylester 5-(tetrahydrofuran-2-ylmethyl) ester

2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3, 5-dicarboxylic acid 3-methylester 5-(5-oxotetrahydrofuran-2-ylmethyl) ester

(S)-2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3, 5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

(R)-2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3, 5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

4-(2-Bromophenyl)-2,6-dimethyl pyridine-3, 5-dicarboxylic acid 3-methylester 5-(tetrahydrofuran-2-ylmethyl) ester

2,6-Dimethyl-4-(3-nitrophenyl)-pyridine-3, 5-dicarboxylic acid3-isopropyl ester 5-(2-methoxyethyl) ester

2,6-Dimethyl-4-(2-nitrophenyl)-pyridine-3, 5-dicarboxylic acid 3-methylester 5-isobutyl ester

2,6-Dimethyl-4-(3-nitrophenyl) pyridine-3, 5-dicarboxylic acid 3-ethylester 5-methyl ester

2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3, 5-dicarboxylic acid dimethylester

4-[2-(2-tert-Butoxycarbonylvinyl)-phenyl]-2,6-dimethyl pyridine-3,5-dicarboxylic acid diethyl ester

2,6-Dimethyl-4-(3-nitrophenyl) pyridine-3, 5-dicarboxylic acid 3-methylester 5-(N-methylbenzylamino)ethyl ester

4-(2,3-Dichlorophenyl)-2,6-dimethyl pyridine-3, 5-dicarboxylic acid3-ethyl ester 5-methyl ester

2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3, 5-dicarboxylic acid 3-methylester

2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3, 5-dicarboxylic acid

2-(2-Aminoethoxy)methyl-4-(2-chlorophlnyl)-6-methyl pyridine-3,5-dicarboxylic acid 3-ethyl ester 5-methyl ester

2,6-Dimethyl-4-(3-nitrophenyl) pyridine-3, 5-dicarboxylic acid3-(2-methoxyethyl) ester 5-(3-phenyl)propen-2-yl ester

2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3, 5-dicarboxylic acid3-(2-dimethylaminoethyl) ester 5-methyl ester (dihydrobromide)

2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3, 5-dicarboxylic acid3-(2-diethylaminoethyl) ester 5-methyl ester (dihydrochloride)

2,6-Dimethyl-4-phenylpyridine-3, 5-dicarboxylic acid dimethyl ester

2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3, 5-dicarboxylic acid3-(3-dimethylaminopropyl) 5-methyl ester (dihydrochloride).

2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3, 5-dicarboxylic acid 3-methylester 5-(N-morpholino)ethyl ester (dihydrochloride)

2,6-Dimethyl-4-(2-nitrophenyl)pyridine-3,5-dicarboxylic acid 3-methylester 5-[1,3-di(N-morpholine)isopropyl] ester trihydrochloride

The compounds corresponding to formula (Ia, examples 1-30) could, in ageneral method, be prepared by oxydation of 1,4-dihydropyridinescorresponding to formula (II). In some cases, when X═2—NO₂, manydihydropyridines II could be rather unstable, so products had to beobtained through Ib and III, (Scheme I), allowing the preparation of newderivatives Ic. In the scheme, X, R and R′ are like have been definedbefore, and R″, although differentiated for clarity in the scheme,should be taken as defined for R.

The 1,4-dihydropyridine derivatives (II) are either already known, orcould be prepared by the standard procedures described in theliterature.

As oxydation agents for preparation of the compounds (a) it is possibleto use all described for standard oxydation procedures, as oxygen,NaNO₂/NOAc, NaNO₂/HCl, HNO₃, Fe(NO₃)₃ or Cu(NO₃)₂, Br₂+NaAcO, CrO₃,sulphur, KMnO₄, chloranyl or o-chloranyl, 2,3-dihydro-5,6-dicyano-1,4-benzoquinone (DDQ), Pd/C, pyridinium chlorochromateadsorbed on alumina (PCC/Al₂O₃), pyridinium dichromate, MnO₂, etc.Controlled ester hydrolysis of Ia, to produce Ib, activation through IIIand esterification to Ic are described in the present report.

The pharmaceutically acceptable salts obtained by addition of acid tothe compounds (I) are prepared by conventional methods, by treatment ofa solution or suspension of the free base (I) with one or twoequivalents of a pharmaceutically acceptable acid, either organic orinorganic. To give some examples, it is possible to mention thefollowing acids: hydrochloric, hydrobromic, sulphuric, phosphoric,acetic, citric, oxalic, malonic, salicylic, malic, lactic,p-toluenesulphonic, gluconic, fumaric, succinic, ascorbic, maleic,methanesulphonic and benzenesulphonic. The obtained salts can show someadvantages, particularly in relation with higher solubility in polarsolvents as water. This can facilitate the preparation of galenic formsrequiring the administration of the product dissolved in water.

The mixtures of diastereomers or enantiomers can be separated using thedifferences of physico-chemical properties of the products, through theusual methods as fractional crystallisation, chromatography, reactionswith asymmetric induction, or by the action of enzymes ormicro-organisms.

The present inventors had put in evidence the fact that the pyridinecompounds with formula (I), according the present invention, have acardioprotective activity and thus, can be used as cardioprotectiveagents. In addition, another object of the present invention consists inpharmaceutical preparations containing at least, one compound of formula(I), as previously defined, or one of its pharmaceutically acceptablesalts.

The compounds of formula (I) according the invention can be administeredalone but, in general, they would be administered as a mixture with aselected pharmaceutical excipient, depending of thr route ofadministration and the standard pharmaceutical practice. As an example,they can be administered by oral route, either in the form of tablets,containing excipients as starch or lactose, or in capsules, either aloneor mixed with excipients, or in the form of syrups or suspensions,containing colour or aromatic substances. They can also be injected byparental route, as by example, by intramuscular, intravenous orsubcutaneous route. When administered by parenteral route, they will bepreferably used in the form of sterile aqueous solution, which cancontain other solutes, as for instance, salt or glucose, to render thesolution isotonic.

The pharmaceutical compositions according the invention could contain aquantity of any of the products with general formula (I) in the way thelevel of the administered dose being between 0.01 and 20 mg/kg. Thedaily dose of the active principle depends of the administration route.In general, an oral dose between 5 and 1000 mg/day will be used.

While when administered intramuscular route, the product can be given inone dose or divided up to three doses, when intravenously administeredthe product can be included into a dropwise system, for continuoussupply. There will be necessarily variations depending of the weight andconditions of the patient, as well as of the administration routechosen.

In that way, the pharmaceutical compositions according the presentinvention, can be used as new drugs for the prevention or treatment ofcardiovascular diseases, as cardiomyopaties, myocardium infarction,angina, cardiac failures, coronary vasospasm, valvular heart disease,etc.

The present invention will be illustrated in reference to some examplesof preparation of compounds according the invention, as well as theresults of the tests of toxicity and pharmacological activity.

Example 1 2,6-Dimethyl-4-phenyl pyridine-3,5-dicarboxylic acid dimethylester

Over a suspension of 119 g (0.1 mol) of pyridinium chlorochromateabsorbed on alumina in 330 ml of CH₂Cl₂, 10 g (0.033 mol) of2,6-dimethyl-4-phenyl-1,4-dihydropyridine-3,5-dicarboxylic acid dimethylester were portionwise added with stirring. The mixture was maintainedwith stirring at room temperature for 8 hours. The remaining solid waseliminated by filtration, and the liquid was washed with water (3×500ml), dried over anh. Na₂SO₄, and concentrated at reduced pressure, todryness. The product was obtained as a solid, (mp 133-5° C., MeOH) witha yield of 75%.

Analysis Calculated for C₁₇H₁₇NO₄

% C % H % N Calc. 68.22 5.72 4.68 Obs. 68.09 5.63 4.64

Example 2 2,6-Dimethyl-4-phenyl-pyridine-3,5-dicarboxylic acid 3-methylester 5-(tetrahydrofuran-2-ylmethyl) ester

A) 2,6-Dimethyl-4-phenyl-1,4-dihydropyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 20 g (0.10 mol) of methyl benzylideneacetoacetate and18.14 g (0.10 mol) of (tetrahydrofuran-2-ylmethyl)-3-aminocrotonate in100 ml of 2-propanol was refluxed with stirring along 24 hours. Thesolvent was evaporated at reduced pressure, and the residue obtained wascrystallised in 15 ml of diisopropylether. A white solid was obtained(mp 117-9° C., diisopropylether) with a yield of 82%.

B) 2,6-Dimethyl-4-phenyl-pyridine-3,5-dicarboxylic acid 3-methyl ester5-(tetrahydrofuran-2-ylmethyl) ester

A mixture of 8 g (0.022 mol) of2,6-dimethyl-4-phenyl-1,4-dihydropyridine-3,5-dicarboxylic acid 3-methylester 5-(tetrahydrofuran-2-ylmethyl) ester, obtained as described in A),and 2.15 g (0.025 mol) of MnO₂ suspended in 15 ml ofmethylisobutylketone was refluxed with stirring along 14 hours. Theremaining solid was filtered of, and the solution obtained wasconcentrated at reduced pressure. The residue obtained was thendissolved in 15 ml of aq HCl 5%, washed with EtAcO (20 ml), and theaqueous phase was taken to pH 8 with aq K₂CO₃ 20%. Then, the aqueousphase was extracted with EtAcO (2×50 ml) and the organic extracts weredried (anh. Na₂SO₄) and concentrated to dryness under vacuum. An oil wasobtained, which crystallised in diisopropylether (2 ml), producing awhite solid (45-7° C., diisopropylether) with a yield of 59%.

Analysis Calculated for C₂₁H₂₃NO₅.

% C % H % N Calc. 68.28 6.28 3.79 Obs. 68.03 6.26 3.85

Example 3 2,6-Dimethyl-4-(3-fluorophenyl) pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A) 2,6-Dimethyl-4-(3-fluorophenyl) 1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 25 g (0.11 mol) of methyl 3-fluoro-benzylideneacetoacetateand 20.84 g (0.11 mol) de (tetrahydrofuran-2-ylmethyl)-3-aminocrotonatein 110 ml of abs. ethanol was refluxed with stirring for 8 hours. Then,the solvent was evaporated under vacuum, up to 60 ml and the mixture wascooled to −10° C.; a precipitate was obtained and on filtration, theproduct was obtained as a clear yellow solid, with a m.p. of 118-20°C.(EtOH), and with a yield of 88%.

B) 2,6-Dimethyl-4-(3-fluorophenyl) pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

To a solution of 8 g (0.021 mol) of 2,6-dimethyl-4-(3-fluorophenyl)1,4-dihydropyridine-3,5-dicarboxylic acid 3-methyl ester5-(tetrahydrofuran-2-ylmethyl) ester, (obtained as indicated before) in20 ml of acetic acid, and with stirring, 2.06 g (0.21 mol) of CrO₃ wereslowly added, with stirring. Once the addition was complete, reflux withstirring was maintained for one hour. Then, the reaction mixture wascooled at room temperature and added to a mixture of 50 ml NH₄OH andice. The resulting solution was then extracted with CH₂Cl₂ (3×100 ml),and the organic extracts were washed with water (250 ml) and dried withanh. Na₂SO₄. Finally, the solvent was evaporated at reduced pressure,and an oil was obtained which crystallised with 5 ml of pentane. Theproduct was obtained as a white solid, of m.p. 66-8° C. (EtOH), with ayield of 65%.

Analysis Calculated for C₂₁H₂₂NFO₅

% C % H % N Calc. 65.11 5.72 3.62 Obs. 65.23 5.95 3.45

Example 4 4-(2-Chlorophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A) 4-(2-Chlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 15 g (0.06 mol) of methyl 2-chlorobenzylideneacetoacetateand 11.64 g (0.06 mol) of (tetrahydrofuran-2-ylmethyl)-3-aminocrotonatein 65 ml of abs ethanol, was refluxed with stirring in the absence oflight, along 18 hours. Then 30 ml of solvent were evaporated, and theremaining solution was cooled to −10° C. In that way, a yellow solid wasobtained (mp 165-7° C., EtOH) with a yield of 86%.

B) 4-(2-Chlorophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A mixture of 8 g (0.02 mol) of4-(2-chlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester, obtainedaccording A) and 71 g (0.059 mol) of pyridinium chlorochromate adsorbedon alumina, was suspended in 200 ml of CH₂Cl₂, and the whole mixture wasstirred at room temperature for 5 hours. The remaining solid waseliminated by filtration, and the liquid was washed with water (3×250ml), dried over anh. Na₂SO₄, and concentrated at reduced pressure, todryness. The product was obtained as an oil, which was purified bycolumn chromatography (Silicagel, n-hexane:EtAcO, 8:2) with a yield of66%,

Analysis Calculated for C₂₁H₂₂ClNO₅

% C % H % N Calc. 62.46 5.49 3.47 Obs. 62.43 5.57 3.59

Example 5 4-(3-Chlorophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A) 4-(3-Chlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 15 g (0.06 mol) of methyl 3-chlorobenzylideneacetoacetateand 11.64 g (0.06 mol) of (tetrahydrofuran-2-ylmethyl)-3-aminocrotonatein 65 ml of abs. ethanol, was refluxed with stirring and in the absenceof light, for 8 hours. Then, the reaction mixture was cooled to −10° C.and a white solid precipitated (137-9° C., MeOH) with a yield of 87%.

B) 4-(3-Chlorophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A mixture of 8 g (0.02 mol) de4-(3-chlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester, obtainedaccording A), and 71 g (0.059 mol) of pyridinium chlorochromate absorbedon alumina, was suspended in 200 ml of CH₂Cl₂. Then, the whole mixturewas maintained with stirring at room temperature, along 8 hours. Theremaining solid was eliminated by filtration, and the liquid was washedwith water (3×250 ml). dried over anh. Na₂SO₄, and concentrated atreduced pressure, to dryness. The product was obtained as an oil, whichwas purified by column chromatography (Silicagel, n-hexane:EtAcO, 8:2)with a yield of 70%.

Analysis Calculated for C₂₁H₂₂CINO₅

% C % H % N Calc. 62.46 5.49 3.47 Obs. 62.40 5.68 3.30

Example 6 4-(2,3-Dichlorophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A) 4-(2,3-Dichlorophenyl)-2,6-dimethyl1,4-dihydropyridine-3,5-dicarboxylic acid 3-methyl ester5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 20 g (0.07 mol) of methyl2,3-dichlorobenzylidenacetoacetate and 13.56 g (0.07 mol) de(tetrahydrofuran-2-ylmethyl) 3-aminocrotonate in 75 ml of abs. ethanolwas refluxed with stirring for 8 hours, in the absence of light. Thereaction mixture was then cooled to −10° C., and the resultingprecipitate was filtered. The product, with a m.p. of 172-3° C. (EtOH),was obtained with a yield of 79%.

B) 4-(2,3-Dichlorophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

To a suspension of 82 g (0.068 mol) of pyridinium chlorochromate onalumina in 230 ml of CH₂Cl₂, 10 g (0.023 mol) of4-(2,3-dichlorophenyl)-2,6-dimethyl 1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester were added, andthe mixture was maintained with strong stirring during 7 hours. Theinsoluble solid was filtered and the remaining liquid was washed withwater (3×250 ml), dried with anh. Na₂SO₄ and concentrated at lowpressure. Finally, the product was obtained as an oil, with a yield of87%.

Analysis Calculated for C₂₁H₂₁Cl₂NO₅

% C % H % N Calc. 57.55 4.83 3.20 Obs. 57.32 5.05 3.08

Example 7 4-(2-Bromophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A) 4-(2-Bromophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 15 g (0.05 mol) of methyl 2-bromobenzylideneacetoacetateand 9.81 g (0.05 mol) of (tetrahydrofuran-2-ylmethyl)-3-aminocrotonatein 55 ml of ethanol, was refluxed in the absence of light for 10 hours.The mixture was then cooled to −10° C., and a yellow solid was obtained(mp 170-2° C., EtOH) with a yield of 85%.

B) 4-(2-Bromophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A mixture of 10 g (0.022 mol) of4-(2-bromophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester, obtained accordingA), and 80 g (0.067 mol) of pyridinium chlorochromate absorbed onalumina, was suspended on 220 ml of CH₂Cl₂, and the mixture was stirredat room temperature for 6 hours.

The remaining solid was eliminated by filtration, and the liquid waswashed with water (3×150 ml), dried over anh. Na₂SO₄, and concentratedat reduced pressure, to dryness. The product was obtained as an oil,which was purified by column chromatography (Silicagel, n-hexane:EtAcO,8:2) with a yield of 66%.

Analysis Calculated for C₂₁H₂₂BrNO₅

% C % H % N Calc. 56.26 4.95 3.12 Obs. 56.21 5.17 3.08

Example 8 4-(3-Bromophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylic acid3-methyl 5-tetrahydrofuran-2-ylmethyl) ester

A) 4-(3-Bromophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylicacid 3,5-di(tetrahydrofuran-2-ylmethyl) ester

A solution of 15 g (0.05 mol) of methyl 3-bromobenzylideneacetoacetateand 9.81 g (0.05 mol) of (tetrahydrofuran-2-ylmethyl)-3-aminocrotonatein 55 ml of abs ethanol, was refluxed with stirring, in the absence oflight, for 10 hours. The reaction mixture was then cooled to −10° C.,yielding a white solid (mp 138-40° C., EtOH) with a yield of 85%.

B) 4-(3-Bromophenyl)-2,6-dimethylpyridine-3,5-dicarboxylic acid3,5-(di(tetrahydrofuran-2-ylmethyl) ester

A mixture of 10 g (0.022 mol) de4-(3-bromophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylic acid3,5-di(tetrahydrofuran-2-ylmethyl) ester obtained as described in A),and 80 g (0.067 mol) of pyridinium chlorochromate adsorbed on alumina,was suspended in 220 ml of CH₂Cl₂, and the suspension was stirred atroom temperature for 5 hours. The insoluble solid was eliminated byfiltration, and the liquid was washed with water (3×200 ml), dried overanh. Na₂SO₄, and concentrated at reduced pressure, to dryness. Theproduct was obtained as an oil, which was purified by columnchromatography (Silicagel, n-hexane:EtAcO, 8:2) with a yield of 74%.

Analysis Calculated for C₂₁H₂₂BrNO₅

% C % H % N Calc. 56.26 4.95 3.12 Obs. 56.62 4.88 3.38

Example 9 2,6-Dimethyl-4-(2-trifluoromethylphenyl)pyridine-3,5-dicarboxylic acid 3-methyl ester5-(tetrahydrofuran-2-ylmethyl) ester

A)2,6-Dimethyl-4-(2-trifluoromethylphenyl)-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 90 ml (118.8 g; 0.68 mol) of2-trifluoromethyibenzaldehyde, 75 ml (79.23 g; 0.68 mol) of methylacetoacetate and 126.38 g (0.68 mol) of(tetrahydrofuran-2-ylmethyl)-3-aminocrotonate in 700 ml of 2-propanol,was refluxed in the absence of light along 10 hours.

Then, 400 ml of solvent were distilled off at reduced pressure, and theremaining solution was cooled at −10° C. In that way, a yellow solid wasobtained (mp 147-9° C., MeOH) with a yield of 69%.

B) 2,6-Dimethyl-4-(2-trifluoromethylphenyl) pyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A mixture of 7 g (0.016 mol) of2,6-dimethyl-4-(2-trifluoromethylphenyl)-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester, obtainedaccording A),

and 57.35 g (0.048 mol) of pyridinium chlorochromate adsorbed onalumina, were suspended on 150 ml of CH₂Cl₂, then the whole mixture wasmaintained with stirring at room temperature for 8 hours. The remainingsolid was eliminated by filtration, and the liquid was washed with water(3×150 ml), dried over Na₂SO₄, and concentrated at reduced pressure, todryness. The product was obtained as an oil, which was purified bycolumn chromatography (Silicagel, n-hexane:EtAcO, 8:2) with a yield of69%.

Analysis Calculated for C₂₂H₂₂F₃NO₅

% C % H % N Calc. 60.41 5.07 3.20 Obs. 60.11 5.31 3.29

Example 10 2,6-Dimethyl-4-(3-trifluoromethylphenyl)pyridine-3,5-dicarboxylic acid 3-methyl ester5-(tetrahydrofuran-2-ylmethyl) ester

A)2,6-Dimethyl-4-(3-trifluoromethylphenyl)-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 13.21 g (0.05 mol) of methyl3-trifluoromethylbenzylideneacetoacetate and 8.99 g (0.05 mol) of(tetrahydrofuran-2-ylmethyl)-3-aminocrotonate in 50 ml of abs ethanol,was refluxed under stirring, and protected from light, for 10 hours. Thesolvent was then evaporated under reduced pressure, and the residue wascrystallised in EtAcO (15 ml). The product was obtained as a white solid(mp 108-10° C., EtOH), with a yield of 88%.

B) 2,6-Dimethyl-4-(3-trifluoromethylphenyl) pyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A mixture of 12 g (0.027 mol) of2,6-dimethyl-4-(3-trifluoromethylphenyl)-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester, obtained asdescribed in A), and 98 g (0.082 mol) of pyridinium chlorochromateadsorbed on alumina, was suspended in 270 ml of CH₂Cl₂, and thesuspension was maintained under stirring at room temperature for 6hours. The remaining solid was eliminated by filtration, and the liquidwas washed with water (3×300 ml), drive over anh. Na₂SO₄, andconcentrated at reduced pressure, to dryness. The product was obtainedas an oil, which was purified by column chromatography (Silicagel,n-hexane:EtAcO, 8:2) with a yield of 65%.

Analysis Calculated for C₂₂H₂₂F₃NO₅

% C % H % N Calc. 60.41 5.07 3.20 Obs. 60.02 5.01 3.51

Example 11 4-(3-Cyanophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A) 4-(3-Cyanophenyl)-2,6-dimethyl 1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 30 g (0.13 mol) of methyl 3-cyanobenzylideneacetoacetateand 24.24 g (0.13 mol) of (tetrahydrofuran-2-ylmethyl)-3-aminocrotonatein 130 ml of abs. ethanol was refluxed with stirring, in the absence oflight, along 8 hours. The reaction mixture was then cooled to −10° C.,and the product was obtained as a yellow solid (mp 127-9° C., EtOH) witha yield of 79%.

B) 4-(3-Cyanophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A mixture of 10 g (0.025 mol) of 4-(3-cyanophenyl)-2,6-dimethyl1,4-dihydropyridine-3,5-dicarboxylic acid 3-methyl ester5-(tetrahydrofuran-2-ylmethyl) ester, obtained as described in A), and91 g (0.076 mol) of pyridinium chlorochromate adsorbed on alumina, wassuspended on 250 ml of CH₂Cl₂, and the suspension was stirred at roomtemperature for 5 hours. The remaining solid was separated byfiltration, and the organic solution was washed with water (3×150 ml),dried with anh. Na₂SO₄, and concentrated to dryness at reduced pressure.The product was obtained as an oil, which was purified by columnchromatography (Silicagel, n-hexane:EtAcO, 8:2) with a yield of 78%.

Analysis Calculated for C₂₂H₂₂N₂O₅

% C % H % N Calc. 66.99 5.62 7.10 Obs. 66.84 5.92 7.14

Example 12 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

To a solution of 30 g (0.07 mol) of2,6-dimethyl-4-(2-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester in 72 ml of aceticacid, heated to reflux, 7.2 g (0.07 mol) of CrO₃ were portionwise added.After the addition was complete, reflux was maintained for oneadditional hour. The reaction mixture was then slowly poured onice-cooled aq NH₄OH (150 ml). The mixture separated in two phases, andit was evacuated with CH₂Cl₂ (3×100 ml). The organic extract was driedwith anh Na₂SO₄, and concentrated to dryness at reduced pressure. Theresulting oil was crystallised in EtAcO-diethylether, yielding a whitesolid (mp 69-70° C., EtOH) with a yield of 79%.

Analysis Calculated for C₂₁H₂₂N₂O₇

% C % H % N Calc. 60.86 5.35 6.76 Obs. 60.63 5.26 6.52

Example 13 (S)-2,6-(Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

Over a stirred solution of 1.183 g (2.84 mmol) of(R/S)-2,6-Dimethyl-4-(2-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(S-tetrahydrofuran-2-ylmethyl) ester in 4 ml ofacetic acid, 588 mg (8.53 mmol) of sodium nitrite was portionwise added,at room temperature. Once the addition completed, the reaction mixturewas maintained with stirring at 50° C., during 90 min. Then, thereaction mixture was poured over 20 ml of ice/water, and then it wasneutralised (to pH 5) with 20% aq NAOH, and then (to pH 7) with NaHCO₃.The solution was then extracted with CH₂Cl₂ (2×25 ml), and the organicextract was washed with a saturated solution of NaCl, dried over anh.Na₂SO₄, and concentrated at reduced pressure, to dryness. The productwas obtained as an oil, which was purified by column chromatography(Silicagel, n-hexane:EtAcO, 1:1). In that way, 879 mg of the productwere obtained (yield:74%). The hydrobromide was prepared by treating anethanolic solution of the product with 48% HBr, obtaining a white solid(121-4° C., EtOH).

Mass Spectra

M/e: 384(4); 368(20); 331(19); 315(25); 284(25); 270(15); 267(27);253(34); 236(42); 235(25); 209(25); 180 (20); 153(28); 152(38); 140(33);139(38); 128(35); 127(43); 126(30); 114(33); 102(23); 101(25); 85 (156);84(543); 77(33); 76(26); 71(1000); 67(35); 55(38).

Example 14 (R)-2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl)ester

Over a solution of 0.89 g (2.13 mmol) of(R/S)-2,6-dimethyl-4-(2-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(R-tetrahydrofuran-2-ylmethyl) ester on 4 ml ofacetic acid, stirred and heated to 60° C., 442 mg (6.41 mmol) of sodiumnitrite was portionwise added. Once the addition was finished, stirringand heating were maintained for 90 min. more. Then, the reaction mixturewas poured over 20 ml of ice/water, and then it was neutralised (to pH5) with 20% aq NAOH, and then (to pH 7) with NaHCO₃. The solution wasthen extracted with CH₂C1₂ (2×25 ml), and the organic extract was washedwith a saturated solution of NaC1, dried over anh. N2₂SO₄, andconcentrated at reduced pressure, to dryness. The product was obtainedas an oil, which was purified by column chromatography (Silicagel,n-hexane:EtAcO, 6:4). In that way, 334 mg of the product were obtained(yield: 38%). The hydrobromide was prepared by treating an ethanolicsolution of the product with 48% HBr, obtaining a white solid (114-6°C., EtOH).

Mass Spectra

M/e:,383(3); 368(16); 331(13); 315(20); 284(21); 270(14); 253(27);236(34); 235(20); 209(20); 180(19); 153(25); 152(33); 140(30); 139(33);128(33); 127(37); 126(27); 102(22); 101(23); 85(149); 84(514); 77(29);76(27); 71(1000); 55(46).

Example 15 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid3-methyl ester 5-(5-oxotetrahydrofuran-2-ylmethyl)ester

A) 2,6-Dimethyl-4-(2-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(5-oxotetrahydrofuran-2-ylmethyl) ester

A solution of 10 g (0,03 mol) of (5-oxotetrahydrofuran-2-ylmethyl)2-nitrobenzylideneacetoacetate and 3.5 g (0,03 mol) of methyl3-aminocrotonate in 30 ml of abs. ethanol, was refluxed with stirring inthe absence of light, along 10 hours. The solvent was then distilled offat reduced pressure, and the obtained residue was purified by columnchromatography (Silicagel, toluene:EtAcO, 1:1). In that way, the productwas isolated as an oil, which crystallised in diisopropylether (5 ml),yielding a yellow solid (mp 86-8° C., diisopropyl ether) with a yield of68%

B) 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid3-methyl ester 5-(5-oxotetrahydrofuran-2-ylmethyl) ester

Over a boiling solution of 15 g (0,035 mol) of2,6-dimethyl-4-(2-nitrophenyl)-1,4-dihydropyridine-3,5dicarboxylic acid3-methyl ester 5-(5-oxotetrahydrofuran-2-ylmethyl) ester, obtainedaccording A), in 35 ml of acetic acid, 3,5 g (0,035 mol) of CrO₃ wasportionwise added with stirring. Once the addition completed, reflux andstirring were maintained for one additional hour. Then, the reactionmixture was poured over 375 ml of conc. NH₄OH with ice, and the mixturewas left overnight at 5° C. In that way, a solid was obtained (mp 132-4°C., MeOH) with a yield of 69%.

Analysis calculated for C₂₁H₂₀N₂O₈

% C % H % N Calc. 58.88 4.71 6.54 Obs. 59.04 4.84 6.59

Example 16 2,6-Dimethyl-4-(3-nitrophenyl) pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A mixture of 15 g (0.036 mol) of2,6-dimethyl-4-(3-nitrophenyl)-1,4-diydropyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester and 130 g (0.108mol) of pyridinium chlorochromate adsorbed on alumina, was suspended on360 ml of CH₂C1₂, and maintained with stirring at room temperature for 8hours. The remaining solid was eliminated by filtration and the organicsolution was washed with water (3×300 ml), dried over anh. Na₂SO₄, andconcentrated to dryness at reduced pressure. The product was obtained asan oil which was purified by column chromatography (Silicagel,n-hexane:EtAcO, 8:2) with a yield of 72%

Analysis calculated for CH₂₁H₂₂N₂O₇

% C % H % N Calc. 60.86 5.35 6.76 Obs. 60.58 5.45 7.01

Example 17 2,6-Dimethyl-4-(3-nitrophenyl)-pyridine-3,5-dicarboxylic acid3,5-di(tetrahydrofuran-2-ylmethyl) ester (hydrochloride)

A) 2,6-Dimethyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylicacid 3,5-di(tetrahydrofuran-2-ylmethyl) ester

A solution of 15 g (0.05 mol) of tetrahydrofuran-2-ylmethyl3-nitrobenzylidenacetoacetate and 8.7 g (0.05 mol) of(tetrahydrofuran-2-ylmethyl)-3-aminocrotonate in 50 ml of abs ethanol,was refluxed with stirring, in the absence of light, along 8 hours. Thereaction mixture was then cooled to −10° C. A yellow soild (mp 122-3°C., EtAcO) was obtained with a yield of 80%.

B) 2,6-Dimethyl-4-(3-nitrophenyl)-pyridine-3,5-dicarboxylic acid3,5-di(tetrahydrofuran-2-ylmethyl) ester (hydrochloride)

A mixture of 8 g (0.016 mol) of2,6-Dimethyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid3,5-di(tetrahydrofuran-2-ylmethyl) ester, obtained as described in A),and 60 g (0.049 mol) of pyridinium chlorochromate adsorbed on alumina,was suspended in 160 ml of CH₂C1₂, and the mixture was maintained atroom temp. with stirring for 6 hours. The solid was separated byfiltration and the liquid was washed with water (3×200 ml), dried (anhNa₂SO₄), and concentrated at reduced pressure. The residue, obtained asan oil, was converted into hydrochloride by dissolving it into ethanol(10 ml) and then, adding HC1 saturated ethyl ether (20 ml). The produceprecipitated as a white solid (mp 75-77° C., EtOH-ether) with a yield of67%.

Analysis calculated for C₂₅H₂₈N₂O₈HC1

% C % H % N Calc. 57.64 5.61 5.38 Obs. 57.75 5.65 5.27

Example 18 4-(4-Chloro-3-nitrophenyl)-2,6-dimethylpyridine-3,5-dicarboxylic acid 3-methyl ester5-(tetrahydrofuran-2-ylmethyl) ester

A)4-(4-Chloro-3-nitrophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 20 g (0.07 mol) of methyl4-chloro-3-nitrobenzylidenacetoacetate and 13.06 g (0.07 mol) of(tetrahydrofuran-2-ylmethyl)-3-aminocrotonate in 70 ml of abs ethanol,was refluxed with stirring, in the absence of light, for 8 hours. Thesolution was then concentrated to dryness at reduced pressure, and theresidue was crystallised in EtAcO. A yellow solid was obtained (mp148-50° C. EtOH) with a yield of 85%.

B) 4-(4-Chloro-3-nitrophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl)ester

A mixture of 9 g (0.020 mol) of4-(4-chloro-3-nitrophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester, obtained asdescribed in A) in 72 g (0.060 mol) of pyridinium chlorochromateadsorbed on alumina, were suspended on 200 ml of CH₂C1₂ then, themixture was maintained with stirring at room temperature for 9 hours.The remaining solid was filtered, and the filtrate was washed with water(3×200 ml), dried with anh. Na₂SO₄, and the solvent evaporated underreduced pressure. The product was isolated as an oil, which was purifiedby column chromatography (Silicagel, n-hexane:EtAcO, 8:2) with a yieldof 69%.

Analysis calculated for C₂₁H₂₁CIN₂O₇

% C % H % N Calc. 56.19 4.72 6.24 Obs. 56.17 4.78 6.59

Example 19 4-(3Acetylaminophenyl)-2,6-dimethyl pyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester (hydrochloride)

A)4-(3-Acetylaminophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 30 g (0.115 mol) of methyl3-acetylaminobenzylideneacetoacetate and 21.27 g (0.115 mol) of(tetrahydrofuran-2-ylmethyl)-3-aminocrotonate in 120 ml of isopropanolwas heated to reflux with stirring along 8 hours, protected form thelight. The solvent was evaporated under vacuum, and the residue wascrystallised in ethyl acetate. A yellow solid was obtained, (MP 158-60°C., meow) with a yield of 76%.

B) 4-(3-Acetylaminophenyl)-2,6-dimethyl pyridine-3,5dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester (hydrochloride)

A mixture of 12 g (0.03 mol) de4-(3-Acetylaminophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester, as indicatedin A), and 4.87 g (0.056 mol) of MnO₂ suspended in 60 ml ofmethylisobutylketone was refluxed with stirring for 24 hours. Theremaining solid was immediately filtered and the solution concentratedat low pressure. The residue obtained was dissolved in 250 ml of 5% aqHC1, the solution was extracted with EtAcO (3×10 ml) and then, pH of theaqueous layer was adjusted to 8 with 20% K₂CO₃. The aqueous phase then,was extracted with CH₂C1₂ (3×100 ml), the organic extracts were driedover anh. Na₂SO₄, concentrated at reduced pressure, and a yellow oil wasobtained, which was transformed in hydrochloride by dissolving it inethanol (10 ml) and adding HC1 saturated diethyl ether (20 ml). In thatway, a white solid was obtained (mp 196-8° C., MeOH) with a yield of59%.

Analysis calculated for C₂₃H₂₆N₂O₆HCI

% C % H % N Calc. 59.67 5.88 6.05 Obs. 59.56 6.12 5.92

Example 20 2,6-Dimethyl-4-(3-hydroxyphenyl) pyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester (hydrochloride)

A) 2,6-Dimethyl-4-(3-hydroxyphenyl) 1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester

A solution of 15 g (0.07 mol) of methyl 3-hydroxybenzylideneacetoacetateand 12.62 g (0.07 mol) of (tetrahydrofuran-2-ylmethyl)-3-aminocrotonatein 70 ml of abs. ethanol, was refluxed with stirring for 8 hours in theabsence of light. The solvent was evaporated at reduced pressure, andthe residue was crystallised in EtAcO. In that way, a yellow solid wasobtained (mp 170-2° C., EtAcO) with a yield of 82%.

B) 2,6-Dimethyl-4-(3-hydroxyphenyl) pyridine-3,5-dicarboxylic acid3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester (hydrochloride)

A mixture of 10 g (0.026 mol) of 2,6-Dimethyl-4-(3-hydroxyphenyl)1,4-dihydropyridine-3,5-dicarboxylic acid 3-methyl ester5-(tetrahydrofuran-2-ylmethyl) ester, obtained as indicated in A), and2.6 g (0.030 mol) of MnO₂ in 50 ml of methylisobutylketone, was refluxedwith stirring for 14 hours. The remaining solid was eliminated byfiltration, and the liquid was concentrated to dryness under reducedpressure. The residue obtained was dissolved in 15 ml of 15% aq. HC1,then, the solution was washed with ethyl acetate (10 ml), the pH wasadjusted to 8 with 20% aq. K₂CO₃. Finally, the solution was extractedwith CH₂C1₂ (2×50 ml), the organic extracts were dried over anh Na₂SO₄,and concentrated to dryness at reduced pressure. The residue appeared asan oil, which crystallised in 2 ml of methanol, and was transformed intothe hydrochloride by dissolution in ethanol (10 ml) and addition of HC1saturated diethyl ether (20 ml). A yellow solid was obtained (mp 95-7°C., MeOH) with a yield of 64%.

Analysis calculated for C₂₁H₂₃NO₆HC1

% C % H % N Calc. 59.79 5.73 3.32 Obs. 59.64 5.66 3.23

Example 21 2,6-Dimethyl-4-(2,3-dimethoxyphenyl)pyridine-3,5-dicarboxylic acid 3-methyl ester5-(tetrahydrofuran-2-ylmethyl) ester

A mixture of 11 g (0,025 mol) of2,6-dimethyl-4-(2,3-dimethoxyphenyl)-1,4-dihydropyridine-3,5-dicarboxylicacid 3-methyl ester 5-(tetrahydrofuran-2-ylmethyl) ester and 92 g (0,076mol) of pyridinium chlorochromate absorbed on alumina, was suspended on250 ml of CH₂C1₂, and the whole mixture was maintained on stirring atroom temperature for 6 hours. The remaining solid was eliminated byfiltration, and the liquid was washed with water (3×300 ml), dried overanh. Na₂SO₄, and concentrated at reduced pressure, to dryness. Theproduct was obtained as an oil, which was purified by columnchromatography (Silicagel, n-hexane:EtAcO, 8:2) with a yield of 79%.

Analysis calculated for C₂₃H₂₇NO₇

% C % H % N Calc. 64.32 6.34 3.26 Obs. 64.34 6.36 3.28

The compounds described in the examples 22 to 30 have been obtained aspreviously described in the literature.

Example 22 2,6-Dimethyl-4-(3-nitrophenyl)-pyridine-3,5-dicarboxylic acid3-isopropyl ester 5-(2-methoxyethyl) ester

Example 23 2,6-Dimethyl-4-(2-nitrophenyl)-pyridine-3,5-dicarboxylic acid3-methyl ester 5-isobutyl ester

Example 24 2,6-Dimethyl-4-(3-nitrophenyl)pyridine-3,5-dicarboxylic acid3-ethyl 5-methyl ester

Example 25 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic aciddimethyl ester

Example 26 4-[2-(2-tert-Butoxycarbonylvinyl)-phenyl]-2,6-dimethylpyridine-3,5-dicarboxylic acid diethyl ester

Example 27 2,6-Dimethyl-4-(3-nitrophenyl) pyridine-3,5-dicarboxylic acid3-methyl ester 5-(N-methylbenzylamino)ethyl ester

Example 28 4-(2,3-Dichlorophenyl)-2,6-dimethyl pyridine-3,5dicarboxylicacid 3-ethyl ester 5-methyl ester

Example 292-(2-Aminoethoxy)methyl-4-(2-chlorophenyl)-6-methylpyridine-3,5-dicarboxylicacid 3-ethyl ester 5-methyl ester

Example 30 2,6-Dimethyl-4-(3-nitrophenyl) pyridine-3,5-dicarboxylic acid3-(2-methoxyethyl) ester 5-(3-phenyl)propen-2-yl ester

Example 31 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid3-methyl ester

A) 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid3,5-dimethyl ester

Over a boiling solution of 3 kg (8.7 mol) of2,6-dimethyl-4-(2nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid3,5-dimethyl ester in 8,251 of acetic acid, 870 g (8.7 mol) of CrO₃ wereportionwise added, with stirring. When the addition was complete, thereaction mixture was refluxed with stirring for one additional hour.When the mixture reached the room temperature, it was slowly poured,with stirring, over 22.5 1 of a mixture of 25% aq. H₄NOH and ice (2:1),and the product precipitated. The solid was isolated by filtration,washed with water until neutral pH, and crystallised (mp 99-101° C.,MeOH) with a yield of 83%.

B) 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid3-methyl ester

A solution of 500 g of2,6-dimethyl-4-(2-nitrophenyl)pyridine-3,5-dicarboxylic acid3,5-dimethyl ester (1.5 mol) and 87.5 g of KOH (1.32 mol) in 5 1 ofmethanol and 1.51 of water, was refluxed with stirring for 4 hours.Then, the solvent was eliminated at reduced pressure and the remainingresidue was triturated with 1 1 of water. The solid (mostly unreactedstarting material) was eliminated by filtration, and the filtrate wastreated, at 0° C., slowly and with stirring, with 100 ml of 35% aq. HC1,and the mixture was maintained with stirring for one additional hourwith stirring, at room temperature. A solid was formed, which was washedwith water (250 ml) and ethanol (250 ml), yielding a yellowish solid (mp232-3° C., ethanol) with a yield of 70%. A small percentage (12%) of thediacid corresponding to example 32, was isolated from the motherliquids.

Analysis calculated for C₁₆H₁₄N₂O₆

% C % H % N Calc. 58.18 4.27 8.48 Obs. 58.30 4.49 8.62

Example 32 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid

Example 33 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid3-(2-dimethylaminoethyl) ester 5-methyl ester (dihydrobromide)

A) Snythesis of5-chlorocarbonyl-2,6-dimethyl-4-(2nitro-phenyl)pyridine-3-carboxylicacid methyl ester

Over a mixture of 2,5 g (7,5 mmol) of 2,6-dimethyl-4-(2-nitrophenyl)pyridine-3,5-dicarboxylic acid 3-methyl ester and 0,7 g (3,8 mmol) ofcianuryl chloride, in 20 ml of anh. acetone under argon atmosphere, 1.1ml of triethylamine were added. The resulting mixture was maintainedwith stirring at room temperature along 7 hours. Then, the mixture wasconcentrated to dryness at reduced pressure, and the residue waspurified by column chromatography (Silicagel, n-hexane:EtAcO, 1:1) witha yield of 80%.

B) 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid3-(2dimethylaminoethyl) ester 5-methyl ester (dihydrobromide) Over amixture of 0,169 (1,8 mmol) of N-dimethylaminoethanol and 0,20 ml oftriethylamine in 8 ml of CH₂C1₂, cooled to 0° C. and in argonatmosphere, 0,5 g (1,5 mmol) of5-chlorocarbonyl-2,6-dimethyl-4-(2-nitro-phenyl)pyridine-3-carboxylicacid methyl ester described in A), dissolved in 4 of CH₂C1₂ were added.The reaction mixture was stirred overnight at room temperature. Then,the mixture was washed with water, dried over anh. Na₂SO₄, andconcentrated to dryness at reduced pressure. The product was obtained asan oil, which was converted in dihydrobromide by treatment with EtOH (10ml) and conc. HBr (1 ml). A white solid was obtained (85-8° C., EtOH)with a yield of 73%.

Analysis calculated for C₂₀H₂₃N₃O₆HBr

% C % H % N Calc. 49.89 5.03 8.73 Obs. 49.62 5.47 9.02

Example 34 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid3-(2-diethylaminoethyl) ester 5-methyl ester (dihydrochloride)

Over a solution of 0,37 g (3,1 mmol) of N-diethylaminoethanol and 0,20 g(2,86 mmol) of triethylamine in 10 ml of CH₂C1₂, cooled to 0° C., andunder nitrogen atmosphere, 1 g (2,86 mmol) of5-chlorocarbonyl-2,6-dimethyl-4-(2-nitro-phenyl)pyridine-3-carboxylicacid methyl ester, obtained as described in A) of the example 33,dissolved in 8 ml of CH₂C1₂, were added. The mixture was stirred at roomtemperature for 15 hours; then, it was washed with water (10 ml), driedover anh. Na₂SO₄, and concentrated at reduced pressure, to dryness. Theproduct was obtained as an oil, which was purified by columnchromatography (Silicagel, EtAcO) and converted into dihydrochloride bytreatment with EtOH (10 ml) and conc. HC1 (1 ml). A white solid wasobtained (166-7° C., EtOH) with a yield of 71%.

Analysis calculated for C₂₂H₂₇N₃O₆2HC1

% C % H % N Calc. 52.68 5.83 8.38 Obs. 52.96 5.56 8.07

Example 35 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid5-(3-dimethylaminopropyl) 3-methyl ester (dihydrochloride)

Over a solution of 0,146 g (1,4 mmol) of 3-dimethylamino-1-propanol and0,13 g (1,29 mmol) of triethylamine in 6 ml of CH₂C1₂, cooled to 0° C.and under nitrogen atmosphere, 0,45 g (1,29 mmol) of5-chlorocarbonyl-2,6-dimethyl-4-(2-nitro-phenyl)pyridine-3-carboxylicacid methyl ester, obtained as described in A) of the example 33,dissolved in 5 ml of CH₂C1₂, were added. The mixture was stirred at roomtemperature along 15 hours; then, it was washed with water (10 ml),dried over anh. Na₂SO₄, and concentrated at reduced pressure, todryness. The product was obtained as an oil, which was purified bycolumn chromatography (Silicagel, acetone) and converted intodihydrochloride by treatment with EtOH (10 ml) and conc. HC1 (1 ml). Awhite solid was obtained (164-6° C., EtOH) with a yield of 75%.

Analysis calculated for C₂₁H₂₅N₃O₆2HC1

% C % H % N Calc. 51.73 5.59 8.62 Obs. 51.50 5.82 8.43

Example 36 2,6-Dimethyl-4-(2-nitrophenyl) pyridine-3,5-dicarboxylic acid3-methyl ester 5-(N-morpholino)ethyl ester (dihydrochloride)

Over a solution of 0,21 g (1,57 mmol) of N-(2-hydroxyethyl)-4-morpholineand 0,15 g of triethylamine in 5 ml of CH₂C1₂, cooled to 0° C. and underargon atmosphere, 0,5 g (1,43 mmol) of5-chlorocarbonyl-2,6-dimethyl-4-(2-nitro-phenyl)pyridine-3-carboxylicacid methyl ester, obtained as described in A) of the example 33,dissolved in 4 ml of CH₂C1₂, were added. The reaction mixture wasstirred at room temperature along 12 hours,; then, it was washed withwater (10 ml), dried over anh. Na₂SO₄, and concentrated at reducedpressure, to dryness. The product was obtained as an oil, which waspurified by column chromatography (Silicagel, EtAcO) and converted intodihydrochloride by treatment with EtOH (10 ml) and conc. HC1 (1 ml). Awhite solid was obtained (mp 96-8° C., EtOH) with a yield of 51%.

Analysis calculated for C₂₂H₂₅N₃O₇2HC1

% C % H % N Calc. 51.25 5.28 8.16 Obs. 51.48 5.11 8.00

Example 37 2,6-Dimethyl-4-(2-nitrophenyl)pyridine-3,5-dicarboxylic acid3-methyl ester 5-[1,3-di(N-morpholine]isopropyl) ester trihydrochloride

A mixture of 0.34 g (0.86 mmol) of5-chlorocarbonyl-2,6-dimethyl-4-(2-nitro-phenyl)pyridine-3-carboxylicacid methyl ester, obtained as described in A) of the example 33, 0.22 g(0.95 mmol) of 1,3-dimorpholin-4-yl-propan-2-ol and 96 mg (0.86 mmol) oftriethylamine, were stirred at room temperature for 12 hours. Then, themixture was washed with water (10 ml), dried over anh. Na₂SO₄, andconcentrated at reduced pressure to dryness. The product was obtained asan oil, which was purified by column chromatography (Silicagel, EtAcO)and converted into trihydrochloride by treatment with EtOH (10 ml) andconc. HC1 (1 ml). A white solid was obtained (mp 187-92° C., EtOH) witha yield of 24%.

Analysis calculated for C₂₇H₃₄N₄O₈3HC1

% C % H % N Calc. 49.83 5.74 8.61 Obs. 49.48 5.61 8.95

PHARMACOLOGICAL AND TOXICOLOGICAL TESTS

The most active compounds of formula (I) of the present invention weresubmitted to pharmacological tests to put in evidence their in vitro andin vivo cardioprotective effects, as well as their hemodynamicproperties and toxicity.

The methods used were the following:

In vitro cardioprotective effect

Isolated guinea-pig ventricular myocytes were obtained following themethod described by Powell et al. (J. Physiol., 1980, 102: 131) asmodified by Levi et al. (J. Physiol., 1990, 425:9P). Cellhypercontracture and death was obtained either by incubation under N₂atmosphere or by incubation with veratridine which induced importantchanges in the ionic homeostase of cardiomyocytes (Hiroko Hashizume etal., European Journal of Pharmacology, 1974, 271: 1-8). Resultsexpressed as percentage of cells protected from hypercontracture i.e.maintaining its rod-shaped morphology with reference to vehicle-treatedcells are given in the tables I and II hereafter.

In order to confirm the cardioprotection, the activity of one of themost interesting compound (example 31 according to the invention) wastested on guinea-pig ventricular cardiomyocytes action potential (AP) inthe presence of veratridine or in anoxic condition. The action potential(AP) time courses of guinea-pig ventricular cardiomyocytes treated withveratridine or made anoxic by incubation under N2 atmosphere weremeasured (patch clamp technique) in absence and presence of the compoundof example 31 according to the invention. This compound does notinfluence significantly the normal action potential but it prevents(100-300 nM) the prolongation of cardiomyocyte action potential durationinduced by veratridine. In anoxic conditions, there is a shortening ofcardiomyocyte action potential duration related mainly with anactivation of K+-ATP dependent current. This effect is inhibiteddose-dependently and strongly by the compound of example 31 according tothe invention (100-300 nM).

TABLE I Percentage of cells protected from hypercontracture obtained byincubation under N2 atmosphere: Compounds (30 nM) according to theexamples: % Protection 12 80 22 63 23 50 24 60 25 50 31 58

TABLE II Percentage of cells protected from hypercontracture obtained byincubation with veratridine: Compounds (1 μM) according to the examples:% Protection 12 57 22 37.5 23 41.3 24 37.5 25 34 31 64

In vivo cardioprotective effect

Cardiac death and arrhythmias were induced by the coronary occlusion andreperfusion method in anaesthetised rats according to the method ofSeyle et al. (Angiology, 1960, 11, 398-407) modified by Krzeminski T.(“proceedings of 7^(th) Freiburg Focus of Biomeasurement”, Strasbourg,16-19 September 1991) Cardiovascular and Respiratory in vivo Studies,Biomesstechnik, Verlag March GmbH, Germany) and according to the LAMBETHconventions (Walker M. J. A. et al., Cardiovasc Re., 1998, 22, 447-455).The products have been administered orally (one day and one hour beforethe experiment). Table III hereafter presents the results obtained. Theyare given in percentage of protection against the mortality and thearrhythmias (ventricular fibrillations).

TABLE III Protective effect in vivo % PROTECTION COMPOUND (2 × 20 mg/kg)% PROTECTION AGAINST ACCORDING TO AGAINST VENTRICULAR EXAMPLE No: DEATHFIBRILLATIONS 12 100 100 22 100 50 23 100 75 24 100 37.5 25 100 50 3185.7 73.4

Hemodynamic effect

The most active compounds according to the invention have been tested inorder to analyse their hemodynamic activity. In anaesthetised rat theintravenous administration of different dosages (30, 100, 300 and 1000mg/kg) of the mentioned compounds did not influence significantly thefollowing parameters: systolic, diastolic and mean arterial bloodpressure, heart rate, ejection time, left ventricular systolic pressure,left ventricular end diastolic pressure dP/dt_(max) and dPdt_(min).,contractility index and relaxation time.

Toxicity

The most active compounds according to the invention present a low peroral toxicity with LD50 more than 2000 mg/kg in the rat.

Conclusion

The pyridyl compounds of formula (i) according to the invention are ableto protect the cardiomycytes against damages induced by ionicmodifications (responsible for most of cardia pathology) and in such away, they are able to protect the treated animals (rats) against deathrelated to cardiac dysfunction and arrhythmia. Consequently, they arepotentially cardioprotective agents in different human cardiac diseases(for example cardiomyopaties, myocardium infarction, angina, cardiacfailures, coronary vasospasm, valvular heart disease, etc.). Moreover,they have a lower per oral toxicity and in therapeutic dosages, they donot present a deleterious hemodynamic activity.

What is claimed is:
 1. A pyridyl compound of the formula.


2. A pyridyl compound of the formula.


3. A composition comprising the compound according to claim 1, incombination with a pharmaceutical excipient.
 4. The compositionaccording to claim 3, wherein said excipient is selected from the groupconsisting of tablets, syrup and a sterile aqueous solution forinjection.
 5. A composition comprising the compound according to claim 2in combination with a pharmaceutical excipient.
 6. The compositionaccording to claim 5, wherein said excipient is selected from the groupconsisting of tablets, syrup and a sterile aqueous solution forinjection.